The present invention relates to a gas discharge display panel using a large number of gas cells in which an inactive gas is sealed and light emission from the cells is caused by interaction between the gas and electrodes included therein, in particular, it relates to a method for driving a gas discharge display panel by using a time division drive.
Recently, display panels are widely used in terminals such as measuring apparatuses, calculators, and computers as a device for displaying figures, letters, and symbols. Light emitting diodes (LEDs), liquid crystals, and discharge cells are among the elements used in such display panels. However, in these applications, it has been found that the quality of a monolithic LED array and the color or light output thereof is not uniform, and that liquid crystals are affected by peripheral brightness, reducing the effectiveness of these elements.
In view of the above, attention has been drawn recently to gas discharge tubes, which can produce a large amount of light emission through molecular interaction with electrodes in the tube, caused by the application of an electric field to a gas sealed within the tube.
In general, a gas discharge panel using many discharge cells containing gas is comprised of two glass plates with parallel electrodes provided inside the glass plates at right angles to each other, and a mixed inactive gas such as neon or argon is contained under pressure between the electrodes, thus forming a discharge tube at a crossing point of the above parallel electrodes. That is, the discharge cells are positioned in a dot arrangement.
When a voltage is applied between both electrodes of the gas discharge cells, a discharge is caused by a reaction of the inactive gas sealed between the electrodes, and the light produced by the discharge is externally output. In particular, in AC type gas discharge cells in which an alternating voltage is applied between the electrodes, when voltage beyond a minimum discharge starting voltage for the discharge cell is applied between the electrodes, discharge is started. The discharge is maintained and the light emission is sustained by wall charges formed in the discharge cell by the first discharge when an alternating voltage having a maximum voltage lower than the discharge voltage is applied.
To reduce the number of drive electrodes needed in such a gas discharge display panel, the panel is driven by time-division, as described in detail later. However, when the gas discharge display panel is driven by the above method, the electrodes of the display panel are multiplexed by the time division during the writing operation, and the voltage is applied to the electrodes via a condenser at each end of the electrode. Therefore, when the voltage applied at both input terminals of an electrode is for example 0 V and 90 V, an intermediate voltage of approximately 45 V sometimes appears on the electrode, because the electrodes are multiplex driven by the condensers. This state is called a half-selection voltage, and is similar to a state in which the voltage application is erased, that is, the wall charges become zero, so that the display point, i.e., the light-emitting point, disappears. In other words, when the voltage applied to, for example selected X electrodes is 140 V and the voltage applied to, for example, Y electrodes, is 0 V, the information may be written. However, if the voltage, for example, 45 V, is applied to the Y electrodes, by half-selection, the voltage difference between the Y electrodes and non-selected X electrodes becomes an erase voltage. Therefore, the light-emitting point, which should be maintained, is erased.
As mentioned above, in the driving circuit of the AC type gas discharge panel, a method has been proposed for decreasing the number of driving circuits by using multiplexed driving, such as a discharge shift system. However, in this method, the driving voltage is high, and thus a high voltage driving circuit is required. Further, when the multiplexing is increased, the operating speed is decreased.